Imaging apparatus and imaging method

ABSTRACT

A lighting unit illuminates an object with at least one type of excitation light and illumination light. An imaging unit captures images with at least one type of fluorescent light generated by the object illuminated with the excitation light, and with reflected light caused when the object reflects the illumination light. A fluorescent light detector generates a delay time distribution image of fluorescent light from a fluorescent light image captured by the imaging unit. A distance measuring unit generates a range image from a reflected light image captured by the imaging unit.

BACKGROUND 1. Technical Field

The present disclosure relates to an imaging apparatus for capturing animage by illuminating an object with light.

2. Description of Related Art

Disclosed in Japanese Patent Unexamined Publication No. 2015-87171 is afluorescent light imaging apparatus for capturing an image withfluorescent light generated by an object illuminated with excitationlight. In Japanese Patent Unexamined Publication No. 2015-87171, adegree of modulation in a change in intensity of fluorescent light and aphase in each of pixels in a fluorescent light image are acquired, phasedifferences between a reference point and other pixels in thefluorescent light image are acquired, fluorescent light components ineach of the pixels in the fluorescent light image are determined, and arelative distance from the reference point is acquired.

SUMMARY

An imaging apparatus according to the present disclosure includes alighting unit and an image acquisition unit. The lighting unitilluminates an object with at least one type of excitation light andillumination light. The image acquisition unit captures images with atleast one type of fluorescent light radiated by the object illuminatedwith the excitation light, and with reflected light caused when theobject reflects the illumination light. The image acquisition unitfurther acquires a delay time distribution image of the at least onetype of fluorescent light, which is generated based on a delay time fromwhen the excitation light enters to when the fluorescent light isradiated.

In an imaging method according to the present disclosure, an object isilluminated with at least one type of excitation light and illuminationlight. Images are further captured with reflected light caused when theobject reflects the illumination light, and with fluorescent lightgenerated by the object illuminated with the excitation light. Based ona result of the captured images, a delay time distribution image of atleast one type of fluorescent light is acquired.

The imaging apparatus according to the present disclosure is capable ofacquiring a delay time distribution image of fluorescent light of anobject from a position away from the object.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view illustrating a specific configuration of animaging apparatus according to a first exemplary embodiment;

FIG. 2 is a flowchart for describing operation of the imaging apparatusaccording to the first exemplary embodiment;

FIG. 3 is a view for describing operation when the imaging apparatusaccording to the first exemplary embodiment illuminates excitationlight;

FIG. 4 is a view for describing operation when the imaging apparatusaccording to the first exemplary embodiment illuminates illuminationlight;

FIG. 5 is a view for describing an example of objects;

FIG. 6 is a view for describing an example of delay time distributionimages of fluorescent light;

FIG. 7 is a view for describing an example of range images;

FIG. 8 is a flowchart for describing operation of an imaging apparatusaccording to a second exemplary embodiment;

FIG. 9 is a view for describing the operation of the imaging apparatusaccording to the second exemplary embodiment;

FIG. 10 is a view for describing another example of illumination timingsignals;

FIG. 11 is a view for describing another example of calculating a delaytime; and

FIG. 12 is a view for describing relations between an imaging wavelengthband and wavelengths of excitation light and illumination light.

DETAILED DESCRIPTION

Exemplary embodiments will be described herein in detail with referenceto the drawings appropriately. However, detailed descriptions more thannecessary might be sometimes omitted. For example, in some cases,detailed description of already well-known items and repeateddescription with respect to substantially the same configuration will beomitted. These omissions are made to avoid unnecessary redundancy of thefollowing description, and to facilitate the understanding of thoseskilled in the art.

Note that the attached drawings and the following description areprovided for those skilled in the art to fully understand the presentdisclosure, and are not intended to limit the subject matter asdescribed in the appended claims. In other words, the exemplaryembodiments that will be described herein each illustrate a specificexample preferable to the present disclosure. Numerical values,components, arrangement and connection of the components, steps, anorder of the steps, etc. shown in the following exemplary embodimentsare mere examples, and are not intended to limit the technology of thepresent disclosure. Among the components in the following exemplaryembodiments, components not recited in any of independent claimsindicating the most generic concept of the present disclosure aredescribed as optional components configuring a preferable exemplaryembodiment.

First Exemplary Embodiment

A first exemplary embodiment will now be described herein with referenceto FIGS. 1 to 7.

[1-1. Configuration]

FIG. 1 is a schematic view illustrating a specific configuration ofimaging apparatus 100 according to the first exemplary embodiment.

As shown in FIG. 1, imaging apparatus 100 according to the presentdisclosure includes lighting unit 110, image acquisition unit 120, andcontroller 130. Image acquisition unit 120 includes imaging unit 121,memory 122, fluorescent light detector 123, and distance measuring unit124.

Lighting unit 110 exclusively illuminates object 200 with at least onetype of excitation light and illumination light. Lighting unit 110includes, for example, a light emitting unit for emitting theillumination light, and another light emitting unit for emitting the atleast one type of excitation light. Lighting unit 110 may be configuredto follow control of controller 130 to cause either of the lightemitting units to emit light. Lighting unit 110 may take anyconfiguration as long as excitation light and illumination light areemitted in a switched manner.

Lighting unit 110 according to this exemplary embodiment emits one typeof excitation light L1 and illumination light L2. Controller 130 selectslight to be emitted per predetermined exposure time (period forcapturing a one-frame image). Lighting unit 110 follows control ofcontroller 130 to illuminate object 200 with the selected light at apredetermined illumination timing.

Illumination light in here refers to light illuminated to object 200 toobserve reflected light reflected by object 200. Excitation light refersto light illuminated to object 200 to cause object 200 to generatefluorescent light. In other words, excitation light refers to lightilluminated to object 200 to observe fluorescent light emitted fromobject 200. In the present disclosure, an image indicative of a delaytime from when excitation light is illuminated to object 200 to whenfluorescent light is emitted is referred to as a delay time distributionimage of fluorescent light. A delay time distribution image offluorescent light is an image having per pixel a value of a time ofdelay, which is caused when fluorescent light is generated, in a time ofarrival to imaging apparatus 100.

In the present disclosure, ultra-violet light (short wavelength light)is used as excitation light L1. Excitation light L1 may be light otherthan ultra-violet light. Excitation light L1 may be light having awavelength that falls around an upper limit of an imaging wavelengthband for imaging unit 121, or light having a shorter wavelength than awavelength that falls within the imaging wavelength band. Visible lightmay be used, for example. An imaging wavelength band refers to a rangeof wavelengths of light with which imaging unit 121 can capture animage.

In the present disclosure, near-infrared light (long wavelength light)is used as illumination light L2. Illumination light L2 may be lightother than near-infrared light as long as the light has a wavelengththat falls within the imaging wavelength band. Illumination light L2 maybe light having a wavelength that falls around a lower limit of theimaging wavelength band for imaging unit 121.

Image acquisition unit 120 receives fluorescent light L3 or reflectedlight L4. Fluorescent light L3 is light radiated by object 200illuminated with excitation light L1. Reflected light L4 is light causedwhen object 200 reflects illumination light L2 illuminated from lightingunit 110. Image acquisition unit 120 performs exposure at an exposuretiming synchronized with an illumination timing in a predeterminedexposure time. Image acquisition unit 120 acquires a delay timedistribution image of fluorescent light and a range image based onfluorescent light L3 and reflected light L4 received in thepredetermined exposure time. In the present disclosure, imageacquisition unit 120 is described as a monochromatic camera (camera forcapturing images with visible light and near-infrared light). Imageacquisition unit 120 internally includes components such as an I/O port,a memory for storing a program, and a processor for executing theprogram.

Imaging unit 121 includes an optical system such as an image sensor anda lens. In this exemplary embodiment, imaging unit 121 includes ascanning CMOS image sensor. Imaging unit 121 captures an image withfluorescent light L3 or reflected light L4 having a wavelength thatfalls within the imaging wavelength band. Imaging unit 121 performs inplural times exposure operations at predetermined exposure timings in anexposure time to capture images. Imaging unit 121 stores the capturedimages in memory 122.

Memory 122 is, for example, a frame memory that is an image signalstorage device configured to store image signals corresponding to aplurality of frames. A semiconductor storage element capable ofoperating at a higher speed, such as a DRAM, is used to configure memory122. Memory 122 may be configured to lie in controller 130, i.e.,outside of image acquisition unit 120.

Fluorescent light detector 123 calculates times of flight (TOF) forexcitation light L1 and illumination light L2 based on imagesrespectively captured by imaging unit 121 with fluorescent light L3 andreflected light L4. Fluorescent light detector 123 calculates a time offluorescence delay based on the TOF for excitation light L1 and the TOFfor illumination light L2. Fluorescent light detector 123 generates adelay time distribution image of fluorescent light based on thecalculated time of fluorescence delay.

Distance measuring unit 124 estimates a distance from imaging unit 121to object 200 based on a plurality of images captured with reflectedlight L4 using a Time Of Flight (TOF) method. Distance measuring unit124 generates a range image of object 200 based on the estimateddistance from imaging unit 121 to object 200. A range image is alsoreferred to as a depth map. A plurality of images captured withreflected light L4 is images captured by imaging unit 121 in an exposureperiod and stored in memory 122.

Controller 130 includes, for example, a non-volatile memory in which aprogram is stored, a volatile memory representing a temporary storagearea for executing the program, an I/O port, and a processor forexecuting the program. Controller 130 selects light to be illuminated bylighting unit 110, and controls a light illumination timing, an exposuretiming for imaging unit 121, and an exposure time representing a lengthof an exposure period. Controller 130 also controls operation offluorescent light detector 123 and distance measuring unit 124.

[1-2. Operation]

Operation (an imaging method) of the imaging apparatus configured asdescribed above will now be described herein with reference to FIG. 2.FIG. 2 is a flowchart for describing operation of imaging apparatus 100according to the first exemplary embodiment.

(Step S201)

Controller 130 uses illumination timing signals to perform controllingso that lighting unit 110 illuminates object 200 with excitation lightL1 at predetermined timings. Lighting unit 110 follows the illuminationtiming signals to illuminate object 200 with excitation light L1. In thepresent disclosure, lighting unit 110 uses ultra-violet light asexcitation light L1.

(Step S202)

Controller 130 controls an exposure operation of imaging unit 121 usingexposure timing signals synchronized with the illumination timingsignals. Controller 130 outputs the exposure timing signals to imagingunit 121. Imaging unit 121 follows the exposure timing signals toperform the exposure operations. In the present disclosure, controller130 outputs two types of exposure timing signals to imaging unit 121. Inother words, imaging unit 121 performs two types of exposure insynchronization with the illumination timing signals for lighting unit110 to capture images with fluorescent light L3.

Operation when imaging apparatus 100 illuminates excitation light willnow be described herein with reference to FIG. 3. FIG. 3 is a view fordescribing operation when imaging apparatus 100 according to the firstexemplary embodiment illuminates excitation light.

FIG. 3 illustrates the operation of imaging apparatus 100 in an exposureperiod ranging from time t0 to time tn.

Illumination timing signals for excitation light shown in FIG. 3represent illumination timing signals used for controlling timings atwhich lighting unit 110 illuminates excitation light. ON and OFF of theillumination timing signals for excitation light represent anillumination state and a non-illumination state, respectively. Changesin intensity of received fluorescent light shown in FIG. 3 represent, asfor fluorescent light L3 radiated by object 200 illuminated withexcitation light L1, time changes in intensity of fluorescent light L3entering into imaging unit 121. FIG. 3 shows first exposure timingsignals and second exposure timing signals for controlling two types ofexposure timings for imaging unit 121. In FIG. 3, ON and OFF of thefirst exposure timing signals and the second exposure timing signalsrepresent a light exposing state and a non-light exposing state ofimaging unit 121, respectively. Images captured at first exposuretimings shown in FIG. 3 are schematic views of images captured inaccordance with the first exposure timing signals. Images captured atsecond exposure timings shown in FIG. 3 are schematic views of imagescaptured in accordance with the second exposure timing signals.

As can be seen from the illumination timing signals for excitation lightshown in FIG. 3, lighting unit 110 repeats operations of illuminationand non-illumination of excitation light L1 per predetermined time d1 inthe exposure period. As described above, in the present disclosure,excitation light is illuminated in plural times for once (one frame)capturing a delay time distribution image of fluorescent light and arange image.

As shown in FIG. 3, imaging unit 121 receives fluorescent light L3generated by object 200 illuminated with excitation light L1. A timingwhen imaging unit 121 receives fluorescent light L3 delays, with respectto an illumination timing for lighting unit 110, by a time obtained byadding a TOF for light reaching object 200 (first delay time) and a timeof occurrence of delayed fluorescent light generated by object 200 inresponse to excitation light L1 (time of fluorescence delay). In theexample shown in FIG. 3, a light receiving timing delays by time d2 froman illumination timing. To detect second delay time (first delaytime+time of fluorescence delay) d2, imaging unit 121 according to thepresent disclosure in here captures images of object 200 in response totwo types of time-modulated exposure timing signals. Imaging unit 121stores the captured images in succession in memory 122.

As shown in FIG. 3, the first and second exposure timing signals are insynchronization with the illumination timing signals for excitationlight. The first exposure timing signals are signals each having a phaseidentical to a phase of each of the illumination timing signals. Forexample, imaging unit 121 performs an exposure operation in a periodranging from time t0 to time t1, during which lighting unit 110illuminates light, while imaging unit 121 does not perform an exposureoperation in a period ranging from time t1 to time t2, during whichlighting unit 110 does not illuminate excitation light. On the otherhand, the second exposure timing signals are signals each having a phaseopposite to the phase of each of the illumination timing signals. Forexample, an exposure operation is not performed in a period ranging fromtime t0 to time t1, during which lighting unit 110 illuminatesexcitation light, while an exposure operation is performed in a periodranging from time t1 to time t2, during which lighting unit 110 does notilluminate light.

As shown in FIG. 3, in a period when exposure is performed in accordancewith a first exposure timing signal, a period during which imaging unit121 receives fluorescent light L3 corresponds to a period between an endof time d2 that has started when the exposure starts and an end of theexposure. Upon imaging unit 121 finishes exposure once, an image isstored in memory 122.

Similarly, as shown in FIG. 3, in exposure in accordance with a secondexposure timing signal, imaging unit 121 receives fluorescent light L3from when the exposure starts. Upon imaging unit 121 finishes exposureonce, an image is stored in memory 122. In this case, in the exposure inaccordance with the second exposure timing signal, fluorescent light L3,which has not yet been received in the exposure in accordance with thefirst exposure timing signal, is received for capturing an image. Inother words, performing exposure twice can securely receive fluorescentlight L3 generated in response to excitation light L1 that has beenilluminated once.

For example, a first delay time might be shorter when object 200 liesnear imaging apparatus 100, and thus an image can more likely becaptured with fluorescent light L3 in exposure in accordance with afirst exposure timing signal. On the other hand, a first delay timemight be longer when object 200 lies away from imaging apparatus 100,and thus an image can more likely be captured with fluorescent light L3in exposure in accordance with a second exposure timing signal. Asdescribed above, performing exposure twice in single illumination canallow fluorescent light L3 to be captured in an image in either or bothof the exposure.

In the exposure period, imaging unit 121 acquires images captured attimings corresponding to the first exposure timings and images capturedat timings corresponding to the second exposure timings respectively innumber corresponding to a number of times of the exposure. Imaging unit121 acquires image A1 from a plurality of the images captured at thefirst exposure timings. Imaging unit 121 also acquires image A2 from aplurality of the images captured at the second exposure timings.

As described above, in an exposure period, illumination of and exposurewith excitation light are repeated in plural times. Fluorescent light L3radiated by object 200 illuminated with excitation light generally has alower intensity. Due to this lower intensity of fluorescent light L3,noise in an image captured with fluorescent light L3 can be problematic.Combining a plurality of images captured with fluorescent light L3 canhowever improve an SN ratio. An intensity of fluorescent light L3 to bereceived by imaging unit 121 can therefore further precisely beestimated. All of a plurality of images captured at first exposuretimings may not be stored in memory 122. For example, a newly capturedimage may be added to an image stored in memory 122 through anarithmetic operation. All of a plurality of images captured at secondexposure timings may not be stored as well.

(Step S203)

After imaging unit 121 starts capturing of an image, controller 130determines whether the exposure time has passed. Controller 130calculates an image capturing time by using a timer or by counting anumber of rectangles of exposure timing signals, for example. Uponcontroller 130 determines that the image capturing time has not yetreached the exposure time, controller 130 returns to step S201. Uponcontroller 130 determines that the image capturing time has reached theexposure time, controller 130 proceeds to step S204.

(Step S204)

Controller 130 calculates a second delay time per pixel in an imagecaptured by imaging unit 121. A second delay time is taken into accountin a range of one cycle of an illumination modulation. In FIG. 3, forexample, one cycle of an illumination modulation refers to time d1ranging from time t0 to time t1. Second delay time d2 shown in FIG. 3 isassociated with a difference between an amount of exposure at a firstexposure timing (amount of light received by imaging unit 121 whileexposure is performed) and an amount of exposure at a second exposuretiming, both of which are acquired in step S202, and respectively havephases different from each other. For example, when second delay time d2is a half of time d1, a difference between an amount of exposure at afirst exposure timing and an amount of exposure at a second exposuretiming is 0. A ratio between the amount of exposure at the firstexposure timing and the amount of exposure at the second exposure timingis at this time 1. As described above, a ratio between time d1 andsecond delay time d2 can be estimated from a ratio between an amount ofexposure at a first exposure timing and an amount of exposure at asecond exposure timing. By acquiring beforehand a relation betweensecond delay time d2 and a difference or a ratio between an amount ofexposure at a first exposure timing and an amount of exposure at asecond exposure timing, and using a result of exposure, second delaytime d2 can be acquired. When acquiring second delay time d2 based on adifference between an amount of exposure at a first exposure timing andan amount of exposure at a second exposure timing, a difference inamount of exposure also depends on a distance to an object. Therefore, asum of an amount of exposure at a first exposure timing and an amount ofexposure at a second exposure timing is used for normalization, oranother measure is performed, and then an association with second delaytime d2 is made.

(Step S205)

Controller 130 uses illumination timing signals for illumination lightto perform controlling so that lighting unit 110 illuminates object 200with illumination light L2 at predetermined timings. Lighting unit 110follows the illumination timing signals for illumination light toilluminate object 200 with illumination light L2. In the presentdisclosure, lighting unit 110 uses near-infrared light as illuminationlight L2.

(Step S206)

Controller 130 controls an exposure operation of imaging unit 121 usingexposure timing signals synchronized with the illumination timingsignals. Controller 130 outputs the exposure timing signals to imagingunit 121. Imaging unit 121 follows the exposure timing signals toperform the exposure operations. In the present disclosure, controller130 outputs two types of exposure timing signals to imaging unit 121. Inother words, imaging unit 121 performs two types of exposure insynchronization with the illumination timing signals for lighting unit110 to capture images with reflected light L4.

Operation when imaging apparatus 100 illuminates illumination light willnow be described herein with reference to FIG. 4. FIG. 4 is a view fordescribing operation when imaging apparatus 100 according to the firstexemplary embodiment illuminates illumination light. FIG. 4 illustratesthe operation of imaging apparatus 100 in an exposure period rangingfrom time t0 to time tn.

Illumination timing signals for illumination light shown in FIG. 4represent illumination timing signals used for controlling timings atwhich lighting unit 110 illuminates illumination light. ON and OFF ofthe illumination timing signals for illumination light represent anillumination state and a non-illumination state, respectively. Changesin intensity of received reflected light represent, as for reflectedlight L4 caused when object 200 reflects illumination light L2, timechanges in intensity of reflected light L4 entering into imaging unit121. FIG. 4 shows first exposure timing signals and second exposuretiming signals for controlling two types of exposure timings for imagingunit 121. In FIG. 4, ON and OFF of the first exposure timing signals andthe second exposure timing signals represent a light exposing state andnon-light exposing state of imaging unit 121, respectively.

Images captured at first exposure timings shown in FIG. 4 are schematicviews of images captured in accordance with the first exposure timingsignals. Images captured at second exposure timings shown in FIG. 4 areschematic views of images captured in accordance with the secondexposure timing signals.

As can be seen from the illumination timing signals for illuminationlight as shown in FIG. 4, lighting unit 110 repeats operations ofillumination and non-illumination per predetermined time d3 in theexposure period. As described above, in the present disclosure,illumination light is illuminated in plural times for once (one frame)capturing a range image. An exposure time when illuminating excitationlight and an exposure time when illuminating illumination light may notbe identical. Exposure times may differ between excitation light L1 andillumination light L2, since an illumination intensity and sensitivityof imaging unit 121 might differ. Similarly, when a plurality of typesof excitation light is used, an exposure time may be changed perexcitation light.

As shown in FIG. 4, imaging unit 121 receives reflected light L4 causedwhen object 200 reflects illumination light L2. A timing when imagingunit 121 receives reflected light L4 delays, with respect to anillumination timing for lighting unit 110, by a TOF for light reachingobject 200 (first delay time). In the example shown in FIG. 4, a lightreceiving timing delays by time d4 from an illumination timing. Todetect first delay time d4, imaging unit 121 according to the presentdisclosure in here captures images of object 200 in response to twotypes of time-modulated exposure timing signals. Imaging unit 121 storesthe captured images in succession in memory 122.

As shown in FIG. 4, the first and second exposure timing signals are insynchronization with the illumination timing signals for illuminationlight. The first exposure timing signals are signals each having a phaseidentical to a phase of each of the illumination timing signals. On theother hand, the second exposure timing signals are signals each having aphase opposite to the phase of each of the illumination timing signals.The first and second exposure timing signals are identical to the firstand second exposure timing signals shown in FIG. 3, and thus will not bedescribed.

As shown in FIG. 4, in a period when exposure is performed in accordancewith a first exposure timing signal, a period during which imaging unit121 receives reflected light L4 corresponds to a period between an endof time d4 that has started when the exposure starts and an end of theexposure. Upon imaging unit 121 finishes exposure once, an image isstored in memory 122.

Similarly, as shown in FIG. 4, in exposure in accordance with a secondexposure timing signal, imaging unit 121 receives reflected light L4from when the exposure starts. Upon imaging unit 121 finishes exposureonce, an image is stored in memory 122. In the exposure in accordancewith the second exposure timing signal, an image is captured withreflected light L4 received at a timing opposite to the timing of theexposure in accordance with the first exposure timing signal. In otherwords, performing exposure twice can securely receive reflected light L4caused when illumination light L2 illuminated once is reflected. Whenillumination light L2 is illuminated, similar to when excitation lightL1 is illuminated, a positional relation between imaging apparatus 100and object 200 allows capturing of an image with reflected light L4through either or both of exposure in accordance with a first exposuretiming signal and exposure in accordance with a second exposure timingsignal.

In the exposure period, imaging unit 121 acquires images captured attimings corresponding to the first exposure timings and images capturedat timings corresponding to the second exposure timings respectively innumber corresponding to a number of times of the exposure. Imaging unit121 acquires image B1 from a plurality of the images captured at thefirst exposure timings. Imaging unit 121 also acquires image B2 from aplurality of the images captured at the second exposure timings. Anormal captured image can be generated using image B1 and image B2.

As described above, in an exposure period, illumination of and exposurewith illumination light are repeated in plural times. Performingillumination and exposure in plural times can improve an SN ratio incapturing images with reflected light L4, similar to when capturingimages with fluorescent light L3. An intensity of reflected light L4 cantherefore further precisely be estimated by imaging unit 121.

(Step S207)

After imaging unit 121 starts capturing of an image, controller 130determines whether the exposure time has passed. Controller 130calculates an image capturing time by using a timer or by counting anumber of rectangles of exposure timing signals, for example. Uponcontroller 130 determines that the image capturing time has not yetreached the exposure time, controller 130 returns to step S205. Uponcontroller 130 determines that the image capturing time has reached theexposure time, controller 130 proceeds to step S208.

(Step S208)

With a procedure similar to a procedure of step S204, controller 130calculates first delay time d4 per pixel in an image captured by imagingunit 121. Similar to step S204, by acquiring beforehand a relationbetween first delay time d4 and a difference or a ratio between anamount of exposure at a first exposure timing and an amount of exposureat a second exposure timing, and using a result of exposure, first delaytime d4 may be acquired.

(Step S209)

Controller 130 acquires a range image and a delay time distributionimage of fluorescent light of object 200 based on second delay time d2acquired in step S204 and first delay time d4 acquired in step S208.Specifically, controller 130 controls distance measuring unit 124 togenerate a range image based on first delay time d4. Distance measuringunit 124 calculates distance D (m) reaching object 200 per pixel togenerate a range image. Distance D can be calculated with D=(d4/2)×lightspeed. Where, a light speed is specified to 299,792,458 (m/s).

Controller 130 also controls fluorescent light detector 123 to generatea delay time distribution image of fluorescent light based on firstdelay time d4 and second delay time d2, both of which have beencalculated per pixel. Fluorescent light detector 123 calculates time offluorescence delay τ per pixel to generate a delay time distributionimage of fluorescent light. Time of fluorescence delay τ can becalculated with τ=d2−d4. The generated range image and the generateddelay time distribution image of fluorescent light are stored in memory122.

The operation of imaging apparatus 100 in one exposure period (oneframe) has been described above. Operation from steps S201 to S209 maybe repeated as required. By repeating the operation in plural times,range images and delay time distribution images of fluorescent light canbe acquired as moving images.

A specific example of this exemplary embodiment will now be describedherein with reference to FIGS. 5 to 7. FIG. 5 is a view for describingan example of objects. FIG. 6 is a view for describing an example ofdelay time distribution images of fluorescent light. FIG. 7 is a viewfor describing an example of range images.

FIG. 5 is the example of the objects for which imaging apparatus 100captures images. Three objects 501 to 503 are assumed to each have adifferent distance from imaging apparatus 100 and a different time offluorescence delay.

FIG. 6 illustrates delay time distribution image of fluorescent light600 formed by capturing and acquiring images of objects 501 to 503 withthe imaging method according to the first exemplary embodiment.Rectangles 601 to 603 respectively are delay time distribution images offluorescent light, which correspond to objects 501 to 503. In FIG. 6,rectangle 603 rendered with a dotted line indicates that object 503 hasnot generated fluorescent light with excitation light L1. Rectangles 601and 602 indicate that objects 501 and 502 have generated fluorescentlight, where object 501 shows a longer time of fluorescence delay.

FIG. 7 illustrates range image 700 formed by capturing and acquiringimages of objects 501 to 503 with the imaging method according to thefirst exemplary embodiment. Rectangles 701 to 703 respectively are delaytime distribution images of fluorescent light, which correspond toobjects 501 to 503. FIG. 7 shows that object 501 lies farthest fromimaging apparatus 100, while object 503 lies nearest to imagingapparatus 100.

As can be seen from FIGS. 6, 7, for example, object 503 lies nearest toimaging apparatus 100, but does not contain a fluorescent material thatgenerate fluorescent light when illuminated with excitation light L1.Also indicated are a fact that object 501 lies farthest from imagingapparatus 100, but generates fluorescent light when illuminated withexcitation light L1, and a time of fluorescence delay in object 501.

[1-3. Effects and Other Benefits]

As described above, in this exemplary embodiment, imaging apparatus 100includes lighting unit 110 and image acquisition unit 120. Lighting unit110 illuminates object 200 with at least one type of excitation light L1and illumination light L2. Image acquisition unit 120 captures imageswith at least one type of fluorescent light L3 generated by object 200illuminated with excitation light L1, and with reflected light L4 causedwhen object 200 reflects illumination light L2. Image acquisition unit120 further acquires a delay time distribution image of the at least onetype of fluorescent light, which is generated based on a delay time forfluorescent light L3 and a delay time for reflected light L4. Imageacquisition unit 120 acquires a range image generated based on the delaytime for reflected light L4.

TOF d2 for excitation light L1 and TOF d4 for illumination light L2 withrespect to object 200 can therefore be calculated.

A calculation process can thus be shared for a TOF for fluorescent lightL3 corresponding to excitation light L1 and a TOF for reflected light L4corresponding to illumination light L2. Time of fluorescence delay τ canalso be measured promptly by illuminating two types of light each havinga different wavelength. This apparatus can be achieved in a simpleconfiguration, since no mechanical switching structure is required.Distance D from imaging apparatus 100 to object 200 can further beacquired based on the TOF for reflected light L4. A time of fluorescencedelay is a characteristic specific to a substance, and can be used tomeasure a characteristic specific to a substance configuring an objectfrom a distant position. Object 200 can thus easily be recognized with adelay time distribution image of fluorescent light.

Similarly, by configuring imaging unit 121 using a color camera,information on a fluorescence spectrum can also be acquired, in additionto a time of fluorescence delay. An image captured with a fluorescencespectrum can be generated with images A1, A2 shown in FIG. 3. In thiscase, recognizing a target and a state is also possible since a time offluorescence delay and a fluorescence spectrum can both be acquired ascharacteristics specific to a substance configuring an object.

Second Exemplary Embodiment

A second exemplary embodiment will now be described herein withreference to FIGS. 8, 9.

[2-1. Configuration]

Imaging apparatus 100 according to the second exemplary embodiment isidentical in specific configuration to the imaging apparatus accordingto the first exemplary embodiment, excluding its operation, which willnow be described herein.

In imaging apparatus 100 according to the second exemplary embodiment,lighting unit 110 exclusively illuminates excitation light andillumination light in an exposure period. The second exemplaryembodiment describes an example when one type of excitation light andillumination light are used. Controller 130 according to the secondexemplary embodiment uses two types of illumination timing signals andfour types of exposure timing signals to control lighting unit 110 andimaging unit 121.

FIG. 8 is a flowchart for describing operation (an imaging method) ofimaging apparatus 100 according to the second exemplary embodiment. FIG.9 is a view for describing the operation of imaging apparatus 100according to the second exemplary embodiment.

FIG. 9 illustrates an example of timing signals for controlling lightingunit 110 and imaging unit 121 in an exposure time. FIG. 9 shows firstillumination timing signals, second illumination timing signals, timingsof changes in intensity of light received by imaging unit 121, firstexposure timing signals, second exposure timing signals, third exposuretiming signals, and fourth exposure timing signals. The timings ofchanges in intensity of received light represent timings at whichintensities of fluorescent light L3 and reflected light L4 entering intoimaging unit 121 change. An intensity and a waveform of light actuallyentering into imaging unit 121 differ between fluorescent light L3 andreflected light L4. FIG. 9 is however schematically illustrated byfocusing on timings at which an intensity of light changes.

[2-2. Operation] (Step S801)

Controller 130 uses illumination timing signals to control lighting unit110. Lighting unit 110 exclusively illuminates object 200 withexcitation light L1 and illumination light L2 in an exposure periodbased on the illumination timing signals. In the second exemplaryembodiment, controller 130 uses two types of illumination timing signalsto control one type of excitation light and illumination light. Lightingunit 110 alternately illuminates excitation light L1 and illuminationlight L2 in the exposure period based on the two types of illuminationtiming signals. As shown in FIG. 9, lighting unit 110 follows a firstillumination timing signal to illuminate object 200 with excitationlight L1 in a period ranging from time t0 to time t1. Next, lightingunit 110 follows a second illumination timing signal to illuminateobject 200 with illumination light L2 in a period ranging from time t2to time t3. Next, lighting unit 110 follows another first illuminationtiming signal to illuminate object 200 with excitation light L1 fromtime t4. As described above, lighting unit 110 follows two types ofillumination timing signals to alternately illuminate excitation lightL1 and illumination light L2.

(Step S802)

Controller 130 uses four types of exposure timing signals to control anexposure operation of imaging unit 121. As shown in FIG. 9, imagingapparatus 100 alternately receives fluorescent light L3 and reflectedlight L4 from object 200.

Imaging unit 121 follows two types of exposure timing signals eachsynchronized with the illumination timing signals and each having adifferent phase to perform four types of exposure per illuminationtiming signal. This is due to a difference between a delay offluorescent light L3 corresponding to excitation light L1 and a delay ofreflected light L4 corresponding to illumination light L2.

At first and second exposure timing signals, images are captured withfluorescent light L3 corresponding to excitation light L1 illuminatedunder the first illumination timing signals. This operation is similarto operation of step S202 in the first exemplary embodiment.

At third and fourth exposure timing signals, images are captured withreflected light L4 caused when illumination light L2 illuminated underthe second illumination timing signal is reflected. This operation issimilar to operation of S206 in the first exemplary embodiment.

(Step S803)

After imaging unit 121 starts capturing of an image, controller 130determines whether the exposure time has passed. Controller 130calculates an image capturing time by using a timer or by counting anumber of rectangles of exposure timing signals, for example. Uponcontroller 130 determines that the image capturing time has reached theexposure time, controller 130 proceeds to step S804, while, uponcontroller 130 determines that the image capturing time has not yetreached the exposure time, controller 130 returns to step S801.

(Step S804)

Controller 130 calculates, per pixel, second delay time p1 forfluorescent light L3. Second delay time p1 is taken into account in arange of one cycle of an illumination modulation (in here, a timeranging from time t0 to time t1). Second delay time p1 is estimatedbased on an amount of exposure at a first exposure timing and an amountof exposure at a second exposure timing. For example, by acquiringbeforehand a relation between second delay time p1 and a difference or aratio between a first amount of exposure and a second amount ofexposure, second delay time p1 may be acquired based on a result ofexposure.

(Step S805)

Controller 130 calculates, per pixel, first delay time p2 for reflectedlight L4. First delay time p2 is taken into account in a range of onecycle of an illumination modulation (in here, a time ranging from timet2 to time t3). First delay time p2 is estimated based on an amount ofexposure at a third exposure timing and an amount of exposure at afourth exposure timing. For example, by acquiring beforehand a relationbetween first delay time p2 and a difference or a ratio between a thirdamount of exposure and a fourth amount of exposure, first delay time p2is acquired based on a result of exposure.

(Step S806)

With a procedure similar to step S209, controller 130 uses fluorescentlight detector 123 and distance measuring unit 124 to generate a rangeimage and a delay time distribution image of fluorescent light.Fluorescent light detector 123 uses first delay time p2 and second delaytime p1 to generate a delay time distribution image of fluorescentlight. Distance measuring unit 124 uses first delay time p2 to generatea range image. The generated range image and the generated delay timedistribution image of fluorescent light are stored in memory 122.

A step to finish a process for one exposure period (one frame) has beendescribed. By repeating steps S801 to S806 as required, range images anddelay time distribution images of fluorescent light can be acquired asmoving images.

[2-3. Effects and Other Benefits]

As described above, in imaging apparatus 100 according to this secondexemplary embodiment, lighting unit 110 exclusively illuminatesexcitation light L1 and illumination light L2 in a predeterminedexposure time. Image acquisition unit 120 captures images withfluorescent light L3 and reflected light L4 each at two types ofexposure timings.

TOF d2 and TOF d4 respectively for excitation light L1 and illuminationlight L2 with which object 200 is illuminated can therefore becalculated in a single exposure time.

A delay time distribution image of fluorescent light and a range imagecan therefore be acquired at an identical timing. When object 200 ismoving, in particular, time changes can occur in magnitude offluorescent light L3 and reflected light L4 in each pixel, and thuserrors might increase in acquiring images with fluorescent light L3 andreflected light L4 respectively at different timings. This tendency issignificant in fluorescent light L3 that will be affected by adifference in delay time between fluorescent light L3 and reflectedlight L4. Imaging apparatus 100 according to the second exemplaryembodiment captures images with fluorescent light L3 and reflected lightL4 at an almost identical timing. Acquiring a delay time distributionimage of fluorescent light and a range image based on images capturedwith fluorescent light L3 and reflected light L4 at an almost identicaltiming can reduce effects caused by factors including when object 200 ismoving.

Other Exemplary Embodiments

As above, the first and second exemplary embodiments have been describedas illustration of the technology disclosed in the present application.However, the technology in the present disclosure is not limited to thefirst and second exemplary embodiments, and can also be applied toembodiments in which change, substitution, addition, omission and thelike are performed. A new exemplary embodiment can also be made by acombination of the components of the first and second exemplaryembodiments.

Accordingly, another exemplary embodiment will be described below. Inthe present disclosure, timings at when a first exposure timing signaland a second exposure timing signal reach ON may at least differ. Afirst exposure timing signal and a second exposure timing signal may besignals each having a phase identical or opposite to a phase of anillumination timing signal. For example, an exposure timing signal mayhave a phase opposite to a phase of an illumination timing signal, whileanother exposure timing signal may have a phase that differs by a ¼cycle, for example, from the phase of the illumination timing signal. Asimilar procedure described below can be achieved with a combination ofexposure timing signals that are in synchronization with an illuminationtiming signal, but each have a shorter cycle. For example, a length of acycle may be extended twice, and four types of exposure timing signalsmay be used to perform an exposure operation. This can also be appliedto a relation between a third exposure timing signal and a fourthexposure timing signal in the second exemplary embodiment. In capturingimages described above, capturing images with using an ultra-violet cutfilter (optical filter) as required for reducing an effect of reflectedlight due to an illumination is advantageous. In the present disclosure,rectangles have been used to describe changes in illumination intensityof lighting unit 110. However, other modulated waveforms can be used toachieve similar or identical effects. FIG. 10 is a view for describinganother example of illumination timing signals. For an illuminationtiming signal, for example, a waveform of an illumination intensity mayhave a shape of a trigonometric function, as shown in FIG. 10. FIG. 10shows illumination timing signals, timings of changes in intensity ofreceived light, first exposure timing signals, and second exposuretiming signals. The illumination timing signals represent signals usedfor controlling timings at which lighting unit 110 illuminatesillumination light L2. The timings of changes in intensity of receivedlight show time changes in intensity of reflected light L4 to bereceived by imaging unit 121. Reflected light L4 represents reflectedlight caused when lighting unit 110 illuminates object 200 withillumination light L2. In FIG. 10, a height of each of the illuminationtiming signals represents an intensity of illumination light L2. In thefirst exposure timing signals and the second exposure timing signalsshown in FIG. 10, upper sides of rectangles each represent a lightexposing state, while lower sides each represent a non-light exposingstate.

In the present disclosure, a first delay time for reflected light and asecond delay time for fluorescent light have been acquired inassociation with a difference or a ratio between two types of exposuretiming signals each having a different time phase. However, anothermethod may be used to acquire a delay time.

Another method for acquiring a delay time will now be described hereinwith reference to FIG. 11. FIG. 11 illustrates illumination timingsignals, timings of changes in intensity of received light, and timingsfor counter. The illumination timing signals represent timings at whichlighting unit 110 illuminates illumination light L2 and excitation lightL1. The timings of changes in intensity of received light schematicallyrepresent timings when an intensity of reflected light L4 or fluorescentlight L3 received by imaging unit 121 changes. The timings for counterrepresent timings when counter signals for counting a delay time change.A cycle of counting counter signals is set in here fully shorter than anemission cycle and a delay time. Imaging unit 121 performs exposure whena counter signal is in an ON state only, in an OFF state only, or inboth the ON and OFF states. In measuring a delay time, a number ofcounts counted until an amount of exposure exceeds a predeterminedamount is determined as the delay time. The example in FIG. 11 assumesthat an amount of received light is measured from time to, and theamount of received light exceeds a predetermined amount at time t4. Inthis case, a delay time is determined to time s1 corresponding to twocycles of the counter. After a delay time has been determined for eachof illumination, a fluorescent light image and a range image can beacquired, similar to the procedures in the first and second exemplaryembodiments. A circuit capable of measuring a time may be used as areplacement to a counter method.

In the present disclosure, one type of excitation light has been usedfor description. However, two types or more of excitation light (shortwavelength illumination) may be used in a switched manner. In this case,a different illumination timing signal may be used in accordance with atype of excitation light. An operation similar to the operation when onetype of excitation light is used is performed per excitation light toacquire a delay time distribution image of fluorescent light. When aplurality of fluorescent materials is present in an object, use of aplurality of different types of illuminations can therefore be likely tohighly effectively emit fluorescent light using one of theilluminations.

In the first exemplary embodiment, excitation light and illuminationlight are illuminated at different timings. However, excitation lightand illumination light may be illuminated at an identical timing (evenwith opposite phases). In this case, in imaging unit 121, a delay timedistribution image of fluorescent light and a range image may beacquired by optically separating (wavelength separation) and acquiringfluorescent light and reflected light acquired from an object. This canbe achieved by providing, for example, in part of a color filter of acolor camera such as a Bayer array camera, a filter that cuts lighthaving a wavelength that falls within a fluorescent wavelength band, butthat allows near-infrared light to transmit. In this configuration, adelay time for fluorescent light is acquired from a pixel into whichlight enters through an RGB filter. A delay time for reflected light isfurther acquired from a pixel into which light enters through anear-infrared filter that blocks visible light. A delay timedistribution image of fluorescent light and a range image are acquiredbased on a delay time for fluorescent light and a delay time forreflected light. A plurality of imaging devices using dichroic mirrorsor dichroic prisms may in here be used to configure an imaging unit,instead of using a Bayer array color camera. In this configuration, byonly using two types of exposure timing signals as shown in FIG. 3 inexposure in a period corresponding to one frame, a delay timedistribution image of fluorescent light and a range image cansimultaneously be acquired.

In the present disclosure, two dimensional images have been used todescribe images captured and generated by imaging unit 121. However, thepresent disclosure can apply one dimensional images (line images) andimages containing only one pixel to acquire similar effects.

A monochromatic camera has been assumed to describe imaging unit 121according to this exemplary embodiment. However, capturing images usinga color camera or a multi-band camera can acquire similar effects. Inthis case, in step S202, capturing images with fluorescence spectra inaccordance with a number of wavelength bands in the color camera can beachieved. Three types of information, i.e., a delay time distributionimage of fluorescent light, a fluorescence spectrum image, and a rangeimage of object 200, can therefore be acquired. A fluorescence spectrumimage refers to an image indicative of an intensity in each of aplurality of wavelength bands of fluorescent light radiated by object200. Since fluorescence spectrum images can be acquired, a plurality ofobjects 200 would be likely to be distinguished with the fluorescencespectrum images, even when delay times of fluorescent light showequality. In other words, since fluorescence spectrum images can beacquired, a higher identification ability of imaging apparatus 100 canbe achieved.

In the present disclosure, after a plurality of types of exposure isperformed, images corresponding in number to a number of times ofexposure are acquired. However, images may be added and stored in asingle memory per exposure, and then an image may be acquired after aplurality of times of exposure.

A relation between wavelengths of excitation light L1 and illuminationlight L2 and an imaging wavelength band for imaging unit 121 will now bedescribed herein with reference to FIG. 12. In FIG. 12, a horizontalaxis shows a wavelength of light. Shorter wavelengths lie on a rightside of the horizontal axis, while longer wavelengths lie on a leftside. In FIG. 12, a vertical axis shows an intensity of light. Visiblelight represents a band of wavelengths, light of which can be viewed byhuman eyes. Imaging wavelength band represents a band of wavelengths,light of which can be captured in images by imaging unit 121.

Upon lighting unit 110 illuminates object 200 with excitation light L1,object 200 radiates fluorescent light L3, as well as emits reflectedlight L5 caused when object 200 reflects excitation light L1. Awavelength of reflected light L5 and a wavelength of excitation light L1are identical to each other. Although it may differ depending on areflection factor of a wavelength of excitation light L1 emitted toobject 200, an intensity of reflected light L5 is generally greater thanan intensity of fluorescent light L3. When lighting unit 110 illuminatesobject with illumination light L2, object 200 reflects illuminationlight L2 and emits reflected light L4. A wavelength of reflected lightL4 and a wavelength of illumination light L2 are identical to eachother. When object 200 illuminated with illumination light L2 radiatesfluorescent light L6, fluorescent light L6 has a wavelength longer thana wavelength of reflected light L4, as well as has an intensitygenerally weaker than an intensity of reflected light L4.

In the first and second exemplary embodiments of the present disclosure,imaging unit 121 (image acquisition unit) captures an image with lighthaving a wavelength that falls within the imaging wavelength band. Theimaging wavelength band represents a band of wavelengths limited bycharacteristics of an image sensor and a filter used in imaging unit121. A wavelength of illumination light L2 is set so as to fall withinthe imaging wavelength band. An advantageous wavelength of excitationlight L1 is one that does not fall within the imaging wavelength band,and shorter than wavelengths that fall within the imaging wavelengthband. Even when fluorescent light L3 and reflected light L5 areilluminated, imaging unit 121 can therefore capture an image withfluorescent light L3 only. Since an intensity of reflected light L5 isgenerally greater than an intensity of fluorescent light L3,non-negligible noise would arise in measuring a delay time forfluorescent light L3. Since a wavelength of excitation light L1 isshorter than wavelengths that fall within the imaging wavelength band,imaging unit 121 can further precisely measure a delay time forfluorescent light L3 having a wavelength that falls within the imagingwavelength band.

Imaging unit 121 may in here include a filter for limiting the imagingwavelength band. As shown in a portion rendered with a broken line onthe imaging wavelength band in FIG. 12, when an imaging wavelength bandincludes a wavelength of excitation light L1, reflected light L5 cancause noise, and thus a delay time for fluorescent light L3 would beless likely to precisely be measured. Use of a filter in imaging unit121 for blocking such a wavelength of excitation light L1 allows imagingunit 121 to further precisely measure a delay time for fluorescent lightL3 having a wavelength that falls within the imaging wavelength band.

When a color filter is used in imaging unit 121 for capturing an image,an imaging wavelength band for imaging unit 121 is limited by the colorfilter. When such a color filter is an RGB filter, imaging unit 121includes a plurality of imaging wavelength bands respectivelycorresponding to colors of the RGB filter. Fluorescent light L3 excitedby excitation light L1 can have various wavelengths depending onsubstances configuring object 200. When imaging unit 121 includes aplurality of different imaging wavelength bands, imaging unit 121 wouldbe able to identify a plurality of types of fluorescent light L3 eachhaving a different wavelength. As described above, when imaging unit 121includes a plurality of imaging wavelength bands, imaging unit 121 maybe configured to acquire delay time distribution images of fluorescentlight, as well as to acquire fluorescence spectra.

Imaging apparatus 100 according to the present disclosure mayadvantageously use ultra-violet light as excitation light L1, andfurther use infrared light as illumination light L2. An advantageouswavelength of illumination light L2 is, in particular, a wavelength ofnear-infrared light that is difficult to see by human eyes, but that canbe detected by an image sensor at relatively higher sensitivity. Anadvantageous wavelength of illumination light L2 is, specifically, 780nm or greater. As shown in FIG. 12, illumination light L2, reflectedlight L4, and fluorescent light L6 to be excited by illumination lightL2 can therefore each have a wavelength that does not fall within avisible light band. Capturing images by imaging apparatus 100 can thusbe less likely to be seen. Use of ultra-violet light as excitation lightL1 can allow excitation light L1 and reflected light L5 to each have awavelength that does not fall within the visible light band. Sinceexcitation light L1 does not have a wavelength that falls within animaging wavelength band for imaging unit 121, measuring a delay timeusing reflected light L5 might be difficult. By using illumination lightL2 having a wavelength that differs from a wavelength of excitationlight, a delay time for reflected light can be measured even whenimaging unit 121 only includes a single imaging wavelength band. Inother words, when a wavelength of excitation light L1 does not fallwithin an imaging wavelength band for imaging unit 121, and a wavelengthof illumination light L2 is longer than a wavelength of visible light,excitation light L1 and illumination light L2 can be less likely to beseen when capturing an image.

A wavelength of fluorescent light L3 to be excited by excitation lightL1 often falls within a visible light band. However, since imaging unit121 captures an image with fluorescent light L3 at higher sensitivity, adelay time distribution image of fluorescent light can be acquired evenwhen an intensity of fluorescent light L3 is weaker. In this case, byreducing an illumination intensity of excitation light L1, fluorescentlight L3 can be less likely to be seen. Lighting unit 110 illuminatesexcitation light L1 or illumination light L2 at a predeterminedillumination timing, and imaging unit 121 repeats exposure at anexposure timing synchronized with the illumination timing in apredetermined exposure time. An SN ratio can therefore be kept higher,and an image can be captured with fluorescent light L3 at highersensitivity. Imaging unit 121 may change a predetermined exposure timebetween when lighting unit 110 illuminates excitation light L1 and whenlighting unit 110 illuminates illumination light L2. Higher sensitivityof imaging unit 121 with respect in particular to fluorescent light L3can therefore be achieved.

Imaging unit 121 may estimate an intensity of fluorescent light L3radiated from object 200 based on a difference between an image capturedby illuminating excitation light L1 for a period equal to or longer thana delay time for fluorescent light L3 and an image captured withoutilluminating excitation light L1.

Functional components (functional blocks) in an imaging apparatusaccording to the present disclosure may be implemented as single chipsrespectively, or a single chip may incorporate some or all of thefunctional blocks, by means of a semiconductor device such as anintegrated circuit (IC) or Large Scale Integration (LSI). A method ofimplementing integrated circuitry is not limited to LSI, andimplementation by means of dedicated circuitry or a general-purposeprocessor may also be used. A field programmable gate array (FPGA) forwhich programming is possible after LSI fabrication, or a reconfigurableprocessor allowing reconfiguration of connections and settings ofcircuit cells within an LSI, may also be used in implementing integratedcircuitry. Further, if a new integrated circuit implementationtechnology comes out to replace the LSI as a result of the developmentof semiconductor technology or a derivative other technology, naturallythe functional blocks may be integrated using that technology. Forexample, application of biotechnology is possible.

Further, all of or a part of various processes described above (e.g.,procedures shown in FIGS. 2, 8) may be implemented by a hardware productsuch as an electronic circuit, or may be implemented by using software.Further, software and hardware may be implemented in a mixed manner forprocessing. It is to be noted that a process using software isimplemented in such a way that a processor in an imaging apparatusexecutes a program stored in a memory. When processing of the abovedescribed exemplary embodiments is implemented with software, some orall of the processing may be performed by separate hardware.

Since the above described exemplary embodiments are for exemplifying thetechnology of the present disclosure, various modifications,replacements, additions, and omissions can be made within the scope ofthe appended claims or of their equivalents.

The present disclosure is applicable to imaging apparatuses.Specifically, the present disclosure is applicable to robot visions andmonitoring cameras.

What is claimed is:
 1. An imaging apparatus comprising: a lighting unitfor illuminating an object with an excitation light and an illuminationlight; and an image acquisition unit for capturing an image of afluorescent light radiated from the object which is illuminated by theexcitation light, and an image of a reflected light from the object,which reflects the illumination light as the reflected light, and forcalculating and acquiring, based on a delay time from when theexcitation light reaches the object to when the fluorescent light isradiated, a delay time distribution image of the fluorescent light. 2.The imaging apparatus according to claim 1, wherein the lighting unitilluminates, in each exposure time that is a time having a predeterminedlength, one of the excitation light and the illumination light at apredetermined illumination timing, and the image acquisition unitcaptures an image of corresponding one of the fluorescent light and thereflected light at an exposure timing synchronized with the illuminationtiming.
 3. The imaging apparatus according to claim 2, wherein the imageacquisition unit changes the exposure time in accordance with lightilluminated by the lighting unit.
 4. The imaging apparatus according toclaim 3, wherein the image acquisition unit captures an image of a lighthaving a wavelength in an predetermined imaging wavelength band, awavelength of the illumination light is in the imaging wavelength bandof the image acquisition unit, and a wavelength of the excitation lightis shorter than the imaging wavelength band of the image acquisitionunit.
 5. The imaging apparatus according to claim 4, wherein theillumination light is near-infrared light, and the excitation light isultra-violet light.
 6. The imaging apparatus according to claim 2,wherein the image acquisition unit captures images of the excitationlight at two exposure timings, and images of the reflected light atother two exposure timings.
 7. The imaging apparatus according to claim6, wherein the image acquisition unit captures an image of a lighthaving a wavelength in an predetermined imaging wavelength band,wavelength of the illumination light is in the imaging wavelength bandof the image acquisition unit, and wavelength of the excitation light isshorter than the imaging wavelength band of the image acquisition unit.8. The imaging apparatus according to claim 7, wherein the illuminationlight is near-infrared light, and the excitation light is ultra-violetlight.
 9. The imaging apparatus according to claim 2, wherein the imageacquisition unit captures an image of a light having a wavelength in anpredetermined imaging wavelength band, wavelength of the illuminationlight is in the imaging wavelength band of the image acquisition unit,and wavelength of the excitation light is shorter than the imagingwavelength band of the image acquisition unit.
 10. The imaging apparatusaccording to claim 9, wherein the illumination light is near-infraredlight, and the excitation light is ultra-violet light.
 11. The imagingapparatus according to claim 1, wherein the lighting unit exclusivelyilluminates the excitation light and the illumination light in eachexposure time, having a predetermined length, at respectivepredetermined illumination timings, and the image acquisition unitcaptures an image of the reflected light or the fluorescent light at anexposure timing synchronized with the corresponding illumination timing.12. The imaging apparatus according to claim 11, wherein the imageacquisition unit captures images of the excitation light at two exposuretimings, and images of the reflected light at other two exposuretimings.
 13. The imaging apparatus according to claim 12, wherein theimage acquisition unit captures an image of a light having a wavelengthin an predetermined imaging wavelength band, wavelength of theillumination light is in the imaging wavelength band of the imageacquisition unit, and wavelength of the excitation light is shorter thanthe imaging wavelength band of the image acquisition unit.
 14. Theimaging apparatus according to claim 13, wherein the illumination lightis near-infrared light, and the excitation light is ultra-violet light.15. The imaging apparatus according to claim 1, wherein the imageacquisition unit calculates, for each pixel, a time of flight (TOF) ofthe illumination light based on the captured image of the reflectedlight, calculates, for each pixel, a TOF of the excitation light basedon the captured image of the fluorescent light, and acquires the delaytime distribution image of the fluorescent light by calculating a timeof fluorescence delay, based on the TOF of the illumination light andthe TOF of the excitation light, for each pixel.
 16. The imagingapparatus according to claim 1, wherein the image acquisition unitcaptures an image of a light having a wavelength in an predeterminedimaging wavelength band, wavelength of the illumination light is in theimaging wavelength band of the image acquisition unit, and wavelength ofthe excitation light is shorter than the imaging wavelength band of theimage acquisition unit.
 17. The imaging apparatus according to claim 16,wherein the illumination light is near-infrared light, and theexcitation light is ultra-violet light.
 18. The imaging apparatusaccording to claim 1, wherein the image acquisition unit acquires afluorescence spectrum image by capturing an image of the fluorescentlight.
 19. An imaging method comprising: illuminating an object with anexcitation light and an illumination light; capturing an image of areflected light from the object, which reflects the illumination lightas the reflected light, and an image of a fluorescent light radiated bythe object which is illuminated by the excitation light; and acquiring adelay time distribution image of the fluorescent light.